First, you have to figure out if your weapon is a sword, spear, or special. Now, raise that smith's level to 4. Finally, you have to go and battle an enemy army, when you do go straight to their main base and kill 500 people and then win the battle. You should will get the 4th weapon at the end of the battle.

First go to the emeny main camp.stay there and fight.Note you have to to command your allies to defend your based.use tactic add 10 min and best with wind nija for for kill 1000.former use 120 attack and 180 attack to kill them faster